Voltage and load compensated flasher

ABSTRACT

A flasher unit comprising a series flasher which is connected in series with the coil of an electromagnetic relay, and a shunttype thermal switch which, in combination with the electromagnetic relay, controls a shunt path around the series flasher for extending the time period during which the contacts of the series flasher are closed. The ON time of the flasher unit corresponds to the combined heating time of the pull member of the series flasher and the period of time during which aforementioned shunt path is closed. The OFF time of the flasher unit corresponds to the cooling time of the pull member of the series flasher.

United States Patent [72] Inventor Hamming G. Siiberg Summitt, NJ. [21] Appl. No. 13,485 [22] Filed Feb. 24, 1970 [45] Patented Oct. 5, 1971 [73] Assignee Wagner Electric Corporation [54] VOLTAGE AND LOAD COMPENSATED FLASHER 10 Claims, 1 Drawing Fig. v

52 us. (:1 335/141 [5i] lnt.Cl... ...H0lh 61/06 [50] Field of Search 335/l4l, 142, 143, [44, 145, [46;337/138 [56] References Cited UNITED STATES PATENTS 2,681,394 6/1954 Hollins 335/14] 2,854,604 9/1958 Milleretalnn 335/141 Primary Examiner-Harold Broome Att0rneyEyre, Mann & Lucas ABSTRACT: A flasher unit comprising a series flasher which is connected in series with the coil of an electromagnetic relay, and a shunt-type thermal switch which, in combination with the electromagnetic relay, controls a shunt path around the series flasher for extending the time period during which the contacts of the series flasher are closed. The ON time of the flasher unit corresponds to the combined heating time ol the pull member of the series flasher and the period of time during which aforementioned shunt path is closed. The ()H" time of the flasher unit corresponds to the cooling time of the pull member of the series flasher.

VOLTAGE AND LOAD COMPENSATED FLASHER The present invention relates to a flasher unit embodying an improvement over the flasher units described in US. Pat. No. 3,364,322 issued on Jan. 16, 1968 to Hemming G. Siiberg. Specifically, the improved flasher unit embodying the present invention eliminates the second set of contacts on the series flasher employed in the units disclosed in the aforementioned patent. An electromagnetic relay is employed to carry out the function of these contacts, providing the advantages of easy adjustment of the flasher unit and elimination of the hazard of thermal overload of the series flasher snap blade, which might result from shorting or excessively high loads.

The preferred embodiment of the present invention disclosed herein employs, as mentioned above, an electromagnetic relay, and a thermoresponsive series flasher and a shunttype thermal switch in combination therewith. These three components are interconnected in such a manner as to cause the ON time of the flasher unit to correspond to the combination of the ON times of the series flasher and the thermal switch, i.e., the ON time of the series flasher is extended by the period of time during which a shunt path around the series flasher is closed, and this period of time corresponds to the ON time of the shunt-type thermal switch. During this period of time, load current is shunted past the series flasher, thereby preventing heating of its pull member. The OFF time of the flasher unit corresponds to the cooling period of the pull member of the series flasher.

A better understanding of the present invention may be had by reference to the drawing of which:

FIG. 1 shows a schematic diagram of the preferred embodiment of the invention.

Referring now specifically to FIG. 1, the flasher unit includes a low-resistance, series-type snap-action flasher 12 which comprises a toggle-action snap blade 14 which has a permanent transverse deformation 15 and is mechanically connected to a mounting member 16 near one end. Thermally expansible pull member 17 is mechanically and electrically connected between the ends of blade 14 so as to deflect the ends of the blade 14 opposite to the direction of deflection caused by the transverse deformation. Blade 14 may have a cutout portion at the locus of the deformation 15, into which cutout portion the pull member 17 will move during the flashing cycle. An adjustable mechanical stop 19 restricts the travel of the free end of blade 14. Moveable contact 18 is mounted on the pull member 17 in cooperative make-and-break relationship with fixed contact 20. Contacts 18 and 20 are normally closed. This series flasher is described in US. Pat. No. 3,470,515 which issued on Sept. 30, 1969 upon an application filed by l-lemming G. Siiberg.

Flasher unit 10 further includes a thermal switch 22 which includes a moveable armature 24, a thermally expansible pull member 26, an insulating bead 28 through which the pull member 26 passes, a mechanical retainer 30 for head 28, normally open fixed and moveable contacts 32 and 34, respectively, and a mounting member 36 to which armature 24 is mechanically connected by a spring member 37, which urges armature 24 toward a position in which contacts 32 and 34 would be closed. One end of the pull member 26 is connected to the moveable contact 34 through a segment of armature 24, and the other end is connected through ballast resistor 38 to fixed contact 20 of series flasher l2. Flasher unit 10 further includes an electromagnetic relay 40 comprising a coil 42 wound about a magnetizable core 44 and an armature 46 carrying a moveable contact 48 which is in cooperative makeand-break relationship with a fixed contact 50. Armature 46 is biased toward the contacts-open position by spring 52 which mechanically connects armature 46 to mounting member 53. An adjustable mechanical stop 54 enables adjustment of the gap between contacts 48, 50 and varies the sensitivity of relay 40 to the current passing through coil 42. Armature 46 is electrically connected to fixed contact 32 of thermal switch 22. Fixed contact 50 of relay 40 is connected to fixed contact 20 of series flasher 12, the latter contact also being connected directly to terminal 56. Terminal 58 is connected through coil 42 to both the snap blade 14 of series flasher 12 and armature 24 of thermal switch 22. In the exemplary circuit shown in FIG. 1, terminal 58 is connected to a source of potential such as a battery B, and terminal 56 is connectable through a switch S through a load L, which may be a lamp load.

The operation of the circuit shown in FIG. I is as follows:

Upon the closing of switch S, currentimmediately flows from battery B through terminal 58, coil 42, snap blade '14, pull member 17, contacts 18, 20 and terminal 56 through switch S to load L, which is thus fully energized. The passage of load current through coil 42 causes armature 46 of electromagnetic relay 40 to be drawn to magnetizable core 44, thus closing contacts 48, 50. However, since contacts 32, 34 of thermal switch 22 remain open, the closing of contacts 48, 50 has no effect on the circuit. The passage of load current through series flasher 12 causes expansion of pull member 17, which results in contacts 18, 20 opening after a period of time. Thus, load L is deenergized, and relay 40 is also deenergized, causing contacts 48, 50 to open.

Now heating current begins to flow from battery B through terminal 58, coil 42 and armature 24 to pull member 26 and through ballast resistor 38, terminal 56, switch S and load L to ground. This heating current is too small to actuate relay 40 or to cause a lamp load to become incandescent, but is effective to raise the temperature of pull member 26, thereby causing it to expand. When pull member 26 has expanded sufficiently, contacts 32, 34 will close. contemporaneously with the foregoing events, i.e., from the time contacts 18, 20 opened, the pull member 17 of series flasher 12 has been cooling. After a period of time generally longer than the period between the openings of contacts 18, 20 and the closing of contacts 32, 34, the contacts 18, 20 will close as a result of the forces exerted on blade 14 by the cooling pull member 17, thereby closing the main load current path. When contacts 18, 20 close, armature 46 of relay 40 is again drawn to magnetizable core 44, thereby closing contacts 48, 50. Since contacts 32, 34 are now closed, there is a closed shunt path around the series flasher 12 from the low-potential terminal of coil 42 through armature 24, contacts 34, 32, armature 46 and contacts 48, 50 to terminal 56. Thus, the very small current flowing through the series flasher 12 cannot cause the pull member 17 to expand. Load L is now fully energized by the larger part of the load current which is being shunted past series flasher 12 and a very small current still passing through he series flasher 12. thus initiating the ON time of flasher unit 10.

With the closing of contacts 18, 20 and 48, 50, the pull member 26 and ballast resistor 38 of thermal switch 22 are also shunted and cooling of the pull member 26 begins. Contacts 32, 34 reopen when the tension exerted by the pull member 26 is sufficient to overcome the magnetic forces exerted on armature 24 by energized coil 42 and 44 of relay 40. At that time, the full load current will again flow through series flasher 12 since the shunt path around flasher 12 is now open. Heating of the pull member 17 of series flasher 12 is thus initiated. When pull member 17 has again expanded sufficiently, the contacts 18, 20 will open, thus terminating the ON period of the flasher unit 10. Thus the OFF period of flasher unit 10, corresponding to the cooling period of pull member 17 of series flasher 12, is initiated. The cycle repeats itself as long as switch S remains closed.

The manner in which the disclosed flasher unit provides for voltage and load compensation can be seen from the foregoing explanation of the operating cycle. When applied voltage rises above the normal or rated voltage of the flasher unit, the overheated pull member of the thermal switch will cause the series flasher to be shunted for a longer-than-normal period of time, after which the series flasher contacts will remain closed for a shorter-than-normal period of time. When applied voltage falls below the normal or rated value of the flasher unit. the underheated pull member of the thermal switch will cause the series flasher to be shunted for a shorter-than-norrnal period of time, after which the series flasher contacts will remain closed for a longer-than-normal period of time. Of course,

voltage or load variations might reduce current levels sufficiently to prevent energization of either the thermal switch 22 or the relay 40 or both, depending upon the individual characteristics and adjustments of these component subassemblies. In any of these three situations, series flasher 12 will operate in substantially the same manner as if it alone were connected between terminals 56 and 58 of the flasher unit.

The advantages of the present invention, as well as certain changes and modifications to the disclosed embodiments thereof, will be readily apparent to those skilled in the art. For example, a number of different series-type flashes might be employed in lieu of flasher 12, which itself may be modified in various ways. For another example, the moveable contact 18 might be mounted on the blade 14, with the pull member 17 being connected to the mounting member 16. Also, various mechanisms might be utilized in place of the disclosed thermal switch 22 or relay 40. It is the applicants intention to cover all -those changes and modifications which could be made to the embodiment of the invention herein chosen for the purposes of the disclosure without departing from the spirit and scope of the invention.

What is claimed is:

l. A voltage and load compensated flasher unit comprising:

1. first and second terminals;

2. first circuit-controlling means having a pair of normally closed contacts which open a first variable period of time after the initiation of steady flow of load current through said circuit-controlling means;

3. second circuit-controlling means comprising:

a. a first pair of normally open contacts, and

b. current-responsive means connected in series with said first circuit-controlling means between said first and second terminals, said current-responsive means being operative to close said normally open contacts in response to a predetermined value of current; and

4. third circuit-controlling means having a second pair of normally open contacts which are closed for a second variable period of time after said normally closed contacts open, a load current shunt path formed by said second and third circuit-controlling means being closed around said first circuit-controlling means when said first and second pairs of normally open contacts are both closed.

2. The flasher unit according to claim 1 wherein the OFF time of said flasher unit corresponds to the time said normally closed contacts are open.

3. The flasher unit according to claim 1 wherein the ON time of said flasher unit corresponds to said second variable period of time plus said first variable period of time.

4. The flasher unit according to claim 1 wherein said first circuit-controlling means is a two-terminal, series-type thermoresponsive snap-action flasher.

5. The flasher unit according to claim 1 wherein said second circuit-controlling means is an electromagnetic relay comprising an armature, one of said first pair of contacts being mounted thereon in cooperative make-and-break relationship with the other of said first pair of contacts, mounting means urging said armature toward a contacts-open position, a mechanical stop associated with said armature, a magnetizable core, and a coil wound around said core.

6. The flasher unit according to claim 5 wherein said coil is urging said armature toward the contacts-open position, and thermally expansible pull means connected between sa|d armature and said second terminal.

8. The flasher unit according to claim 7 wherein a ballast resistor is connected in series with said thermally expansible pull means between said armature and said second terminal.

9. A voltage and load compensated flasher unit comprising:

1. first and second terminals;

2. a two-terminal, series-type thermoresponsive snap-action flasher having normally closed contacts;

3. an electromagnetic relay comprising an armature, a

moveable contact mounted thereon in cooperative makeand-break relationship with a fixed contact which is electrically connected to said second terminal, a magnetizable core, a coil wound around said core, said coil being connected in series with said series flasher between said first and second terminals, and mounting means urging said armature toward a contacts-open position; and

4. a shunt-type thermal switch comprising an armature, a

moveable contact mounted thereon in cooperative makeand-break relationship with a fixed contact which is electrically connected to said relay armature, mounting means for said thermal-switch armature, a thermally expansible pull member which, when cool, maintains said contacts normally open against the bias of said mounting means, and a ballast resistor, said thermal-switch armature being positioned in proximity to said magnetizable core of said relay so as to be subject to the magnetic field of said core, said thermal-switch armature being connected in a series circuit with said relay coil said thermally expansible pull member, and said ballast resistor between said first and second terminals.

10. The flasher unit according to claim 9 wherein;

l. the OFF time of said flasher unit corresponds to the period of time during which the contacts of said seriestype flasher are open, and

2. the ON time of said flasher unit corresponds to the period of time during which the contacts of said shunt-type thermal switch are closed plus the period of time from the initiation of steady flow of load current through said seriestype flasher to the opening of said contacts of said seriestype flasher. 

1. A voltage and load compensated flasher unit comprising:
 1. first and second terminals;
 2. first circuit-controlling means having a pair of normally closed contacts which open a first variable period of time after the initiation of steady flow of load current through said circuit-controlling means;
 3. second circuit-controlling means comprising: a. a first pair of normally open contacts, and b. current-responsive means connected in series with said first circuit-controlling means between said first and second terminals, said current-responsive means being operative to close said normally open contacts in response to a predetermined value of current; and
 4. third circuit-controlling means having a second pair of normally open contacts which are closed for a second variable period of time after said normally closed contacts open, a load current shunt path formed by said second and thirD circuitcontrolling means being closed around said first circuitcontrolling means when said first and second pairs of normally open contacts are both closed.
 2. first circuit-controlling means having a pair of normally closed contacts which open a first variable period of time after the initiation of steady flow of load current through said circuit-controlling means;
 2. the ON time of said flasher unit corresponds to the period of time during which the contacts of said shunt-type thermal switch are closed plus the period of time from the initiation of steady flow of load current through said seriEs-type flasher to the opening of said contacts of said series-type flasher.
 2. a two-terminal, series-type thermoresponsive snap-action flasher having normally closed contacts;
 2. The flasher unit according to claim 1 wherein the OFF time of said flasher unit corresponds to the time said normally closed contacts are open.
 3. The flasher unit according to claim 1 wherein the ON time of said flasher unit corresponds to said second variable period of time plus said first variable period of time.
 3. second circuit-controlling means comprising: a. a first pair of normally open contacts, and b. current-responsive means connected in series with said first circuit-controlling means between said first and second terminals, said current-responsive means being operative to close said normally open contacts in response to a predetermined value of current; and
 3. an electromagnetic relay comprising an armature, a moveable contact mounted thereon in cooperative make-and-break relationship with a fixed contact which is electrically connected to said second terminal, a magnetizable core, a coil wound around said core, said coil being connected in series with said series flasher between said first and second terminals, and mounting means urging said armature toward a contacts-open position; and
 4. a shunt-type thermal switch comprising an armature, a moveable contact mounted thereon in cooperative make-and-break relationship with a fixed contact which is electrically connected to said relay armature, mounting means for said thermal-switch armature, a thermally expansible pull member which, when cool, maintains said contacts normally open against the bias of said mounting means, and a ballast resistor, said thermal-switch armature being positioned in proximity to said magnetizable core of said relay so as to be subject to the magnetic field of said core, said thermal-switch armature being connected in a series circuit with said relay coil, said thermally expansible pull member, and said ballast resistor between said first and second terminals.
 4. The flasher unit according to claim 1 wherein said first circuit-controlling means is a two-terminal, series-type thermoresponsive snap-action flasher.
 4. third circuit-controlling means having a second pair of normally open contacts which are closed for a second variable period of time after said normally closed contacts open, a load current shunt path formed by said second and thirD circuit-controlling means being closed around said first circuit-controlling means when said first and second pairs of normally open contacts are both closed.
 5. The flasher unit according to claim 1 wherein said second circuit-controlling means is an electromagnetic relay comprising an armature, one of said first pair of contacts being mounted thereon in cooperative make-and-break relationship with the other of said first pair of contacts, mounting means urging said armature toward a contacts-open position, a mechanical stop associated with said armature, a magnetizable core, and a coil wound around said core.
 6. The flasher unit according to claim 5 wherein said coil is connected in series with said first circuit-controlling means between said first and second terminals.
 7. The flasher unit according to claim 1 wherein said third circuit-controlling means comprises an armature, one of said second pair of contacts being mounted thereon in cooperative make-and-break relationship with the other of said second pair of contacts, said armature being electrically connected to the junction of said first circuit-controlling means and said current-responsive means of said second circuit-controlling means, said armature being cooperatively positioned with respect to said current-responsive means, mounting means urging said armature toward the contacts-open position, and thermally expansible pull means connected between said armature and said second terminal.
 8. The flasher unit according to claim 7 wherein a ballast resistor is connected in series with said thermally expansible pull means between said armature and said second terminal.
 9. A voltage and load compensated flasher unit comprising:
 10. The flasher unit according to claim 9 wherein; 